1. Field of the Invention
The present invention relates to clock signals. More particularly, the present invention relates to the generation of a clock signal.
2. Description of the Related Art
Cellular radiotelephones are rapidly decreasing in size and cost. In order to accomplish these reductions, the number of parts contained in a radiotelephone are reduced. This reduces the cost of the total number of radiotelephone parts, the manufacturing costs and also reduces the weight of the unit. In order to continue these reductions in cost and weight, the radiotelephone parts count must be reduced further.
Radiotelephones require multiple clock frequencies to operate due to the different requirements of circuits within the radiotelephone. For example, a microprocessor may use a different clock than the RF circuits. Some of these clock frequencies are obtained by dividing one clock signal into sub-multiples of that frequency. This technique reduces the number of oscillators needed to generate the various clock signals.
In a code division multiple access radiotelephone, a master clock frequency of eight times the chip rate of 1.2288 MHz is used for various digital circuits. For cellular use, this frequency, 9.8304 MHz, or its double of 19.6608 MHz, are not suitable master frequencies for the RF components of the radiotelephone since neither is an even multiple of the 30 kHz RF channel spacing required for cellular radio in the United States.
In this case, multiple oscillators are needed to generate the different clock signals required by both the digital hardware and the RF circuitry. There is a resulting need for a clock generator that can produce a clock frequency that is an uneven multiple of another frequency, thus reducing the number of clock synthesizers required.